1. Field of the Invention
In general, the present invention relates to a device, system and method of using a new and improved mud motor. More particularly, the present invention provides a mud motor with a transmission having a torque and thrust transfer coupling with a pull load safety.
2. Description of the Prior Art
A mud motor or drilling motor is typically a progressive cavity positive displacement motor placed in the drill string to provide additional power to the bit while drilling or rotate the drill bit while the drill string is sliding. Mud motors are frequently utilized in directional drilling applications in horizontal wells, but they are also utilized in straight vertical wells where increased performance is desired.
As the desired drill bit motion is purely rotational, a transmission is required to convert the rotation and translation of the mud motor power section rotor to pure rotation at the bit. The motor uses drilling fluid commonly referred to as drilling mud or just mud to create rotating and translating eccentric motion in the power section of the motor, which is transferred as rotating power to the drill bit. In other words, as fluid is driven through the power section of a mud motor, the rotor spins but also translates as the rotor lobes move from one stator cavity to the next.
Because of the curves needed to be built in directional drilling, the transmission in the mud motor must feature a bend angle in its assembly. This bend angle must be accommodated by the mud motor transmission as well as the translate of the power section rotor. Current transmission designs that allow for some degree of bending, generally fall into three categories, a constant velocity, also referred to as a CV joint, jaw clutch coupling, and flex shafts.
Constant velocity joint transmissions very generally utilize cylindrical pockets in the coupling that create the female portion of the coupling interface. Spherical pockets in the shaft hold the balls. The balls allow torque between the coupling and shaft. The spherical thrust reaction interface allows the shaft to rock back and forth relative to the coupling while both rotate together. To complete the assembly, this same coupling to shaft interface is found at each end of the shaft. An advantage is that they may be smooth running and generally an efficient torque transfer. However, a weakness and or limitation are that the point and line contact interfaces generate high stresses in the joint.
Jaw clutch couplings generally provide enough clearance at this interface to allow a three degree misalignment between the sides of the coupling interface. With enough play between the parts, the input end can rotate and translate with the power section and the output end can simply rotate. An advantage may be that they are simple, easily repaired, and have higher damage tolerance. A weakness and or limitation are that they exhibit clunky operations and the point and line contacts generate high stresses in the joint.
The flex shaft coupling relies upon a long shaft. It is generally long enough that it can withstand the three degree misalignment between the input and output and rotate and translate with the power section while keeping stresses low. Since the motion of the power section is a given deflection input, the design principle here is reduce the bending stiffness of a deflecting member to reduce the stress in the deflecting member such that it can survive fatigue loading for an adequate length of time. An advantage may be that they run smooth and are the simplest assembly. A weakness and or limitation are that the shafts must be long to manage fatigue.
Furthermore, expensive exotic materials such as titanium are often used and shafts are still prone to failure in bending fatigue.
The current mud motor transmissions on the market have known torque transfer and life limitation, which limits the drilling industry and prior art attempts at improvements to this problem have not provided the desired solutions. Thus, there is a need for an apparatus, process and or system that provides a new mud motor with an improved transmission. The above discussed limitations in the prior art is not exhaustive. The current invention provides an inexpensive, time saving, more reliable apparatus, method and system where the prior art fails.